Systems and methods for improving power efficiency in refreshing memory banks

ABSTRACT

A memory device may include a phase driver circuit that may output a first voltage for refreshing a plurality of memory cells. The memory device may also include a plurality of word line driver circuits that may receive the first voltage via the phase driver circuit, such that each word line driver circuit of the plurality of word line driver circuits may provide the first voltage to a respective word line associated with a respective portion of the plurality of memory cells. In addition, each word line driver circuit may refresh the respective portion of the plurality of memory cells based on a respective word line enable signal provided to a first switch of the respective word line driver circuit.

BACKGROUND Field of the Present Disclosure

Embodiments of the present disclosure relate generally to the field of memory devices. More specifically, embodiments of the present disclosure relate to refresh operations for memory devices.

Description of Related Art

Electronic devices, such as semiconductor devices, memory chips, microprocessor chips, image chips, and the like, may receive data for storage, operations, analysis, and the like. The data may be stored in memory devices or memory cells (e.g., double data rate fourth-generation synchronous dynamic random-access memory (DDR4)). These memory cells may store the data in capacitors that may lose their charge over time and are refreshed periodically to continue to store the data. These capacitors of the corresponding memory cells may be recharged during a refresh operation.

As the density of components disposed on electronic devices increases, the speed in which electronic devices operate increases, and the sizes of electrical components (e.g., capacitors) decrease, it may be more challenging to perform a refresh operation in memory devices. For instance, in certain types of memory bank designs (e.g., 8 G and 16 G), the amount of time available to perform a refresh operation may be limited due to the number of memory cells present in the memory bank that are to be refreshed. As such, to perform this refresh operation, a number of circuit components (e.g., local phase drivers) may be used to provide refresh currents (e.g., I_(dd5b)) to a number of rows of memory cells in each memory bank within a memory device. However, performing the refresh operation in this manner may involve cycling the number of circuit components on and off for each row of memory cells. This cyclical on and off operation inefficiently uses power while refreshing the memory cells. With this in mind, it is desirable to provide improved systems and methods for refreshing memory cells of a memory device more efficiently.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a simplified block diagram illustrating a semiconductor device that includes a phase driver for refreshing memory cells of memory banks, according to an embodiment of the present disclosure;

FIG. 2 is a schematic diagram illustrating a phase driver coupled to a word line driver for refreshing memory cells that may be part of the semiconductor device of FIG. 1, according to an embodiment of the present disclosure;

FIG. 3 is a schematic diagram illustrating a voltage selector coupled to a phase driver coupled to a word line driver for refreshing memory cells that may be part of the semiconductor device of FIG. 1, according to an embodiment of the present disclosure;

FIG. 4 is a timing diagram illustrating an example refresh operation that refreshes four word lines of a memory bank using one phase driver, according to an embodiment of the present disclosure; and

FIG. 5 is another timing diagram illustrating another example refresh operation that refreshes four word lines of a memory bank using one phase driver, according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

As mentioned above, memory devices, such as dynamic random-access memory (DRAM) chips, may store each bit of data in a memory cell via a capacitor on the chip. As time passes, the charge in the capacitor may dissipate or leak, such that the data (e.g., voltage) of the capacitor (e.g., memory cell) may not accurately represent the data originally stored in the memory cell. To preserve the data stored in the memory cell, external circuitry periodically performs a refresh operation, which may include reading each cell and rewriting the data stored thereon, thereby maintaining the desired voltage or charge on the capacitor.

In some embodiments, circuitry (e.g., refresh pumps) may be used to refresh word lines of the memory cells. By way of example, the circuitry used to refresh word lines may include refresh pumps, which may correspond to on-chip voltage generators capable of providing voltage to respective word lines. As the density of memory banks disposed on a memory device increases, the power used to perform memory refresh operations increasingly contributes to the overall power of the memory device. For instance, row refresh cycle time (tRFC) may be 350 ns on 8 G and 16 G DDR4 memory designs. As such, during the row refresh cycle time (tRFC), a refresh pump may be utilized (e.g., charged and discharged) multiple times to perform refresh operations on different sets (e.g., rows) of memory cells. For example, six refresh pumps may be used to refresh six groups of different rows per bank during one refresh operation. Refreshing these groups of rows may involve turning a phase driver on and off (for each refresh pump) to provide the desired voltage to each refresh pump.

With more and larger memory banks disposed on a memory device, the phase drivers may turn on and off multiple times to perform one refresh operation on each of the memory cells of the memory device. As a result, multiple capacitors are being charged and discharged via each refresh pump. Since each of the refresh pumps is using a different phase driver, the refresh operation amounts to charging a relatively large capacitor due to the capacitance value associated with the components disposed on the phase driver for each refresh operation. Indeed, the power consumed by cycling the phase driver on and off during a refresh operation may amount to 11% of the total power (e.g., Idd5B power) used to refresh the memory device.

With the foregoing in mind, in certain embodiments, the memory device may employ the same phase driver for each of the refresh pumps used to perform a refresh operation for each of the memory cells of a memory bank. As such, the phase driver may charge and discharge one time per refresh operation, as opposed to one time per refresh pump. In this way, the total power consumed by the memory device to perform a refresh operation may be decreased (e.g., 150 mW-200 mW, 3-4% total power savings). Additional details with regard to performing the refresh operation in accordance with the embodiments described herein will be discussed below with reference to FIGS. 1-5.

Turning now to the figures, FIG. 1 is a block diagram of a semiconductor device 10, in accordance with an embodiment of the present disclosure. The semiconductor device 10 may be any suitable memory device, such as an LPDDR4 SDRAM integrated into a single semiconductor chip, for example. The semiconductor device 10 may be mounted on an external substrate 2 that is a memory module substrate, a mother board or the like. The semiconductor device 10 may include a plurality of memory banks, such that each memory bank has a plurality of memory cell arrays 11. Each memory cell array 11 may include a plurality of word lines WL, a plurality of bit lines BL, and a plurality of memory cells MC arranged at intersections of the plurality of word lines WL and the plurality of bit lines BL. The selection of the word line WL is performed by a row decoder 12 and the selection of the bit line BL is performed by a column decoder 13. Sense amplifiers 18 are coupled to corresponding bit lines BL and connected to local input/output (I/O) line pairs LIOT/B. Local IO line pairs LIOT/B are connected to main IO line pairs MIOT/B via transfer gates TG 19 which function as switches.

Turning to the explanation of a plurality of external terminals included in the semiconductor device 10, the plurality of external terminals includes address terminals 21, command terminals 22, data strobe (DQS) terminals 23, data (DQ) terminals 24 and power supply terminals 25 and 26. The data terminals 24 may be coupled to output buffers for read operations of memories. Alternatively, the data terminals 24 may be coupled to input buffers for read/write access of the memories.

The address terminals 21 are supplied with an address signal ADD and a bank address signal BADD. The address signal ADD and the bank address signal BADD supplied to the address terminals 21 are transferred via an address input circuit 31 to an address decoder 32. The address decoder 32 receives the address signal ADD and supplies a decoded row address signal XADD to the row decoder 12, and a decoded column address signal YADD to the column decoder 13. The address decoder 32 also receives the bank address signal BADD and supplies the bank address signal BADD to the row decoder 12 and the column decoder 13.

The command terminals 22 are supplied with a command signal COM. The command signal COM may include one or more separate signals. The command signal COM transmitted to the command terminals 22 is input to a command decoder 34 via the command input circuit 33. The command decoder 34 decodes the command signal COM to generate various internal command signals. For example, the internal commands may include a row command signal to select a word line and a column command signal, such as a read command or a write command, to select a bit line.

Although the address terminals 21 and the command terminals 22 are illustrated in FIG. 1 as being separate terminals, it should be noted that in some embodiments the address input circuit 31 and the command input circuit 33 may receive address signals ADD and command signals COM via one or more address and command terminals. That is, the address signals ADD and command signals COM may be provided to the semiconductor device 10 via the same terminal. For instance, the address and command terminals may provide an address signal at a falling clock edge (e.g., in synchronism with clock falling edge) and a command signal at a rising clock edge (e.g., in synchronism with clock rising edge). With this in mind, it should be understood that the description provided in the present disclosure with the separate address terminals 21 and command terminals 22 is included for discussion purposes and the techniques described herein should not be limited to using separate address terminals 21 and command terminals 22.

Accordingly, when a row address command is issued with an active command, the row may be active and a write or read command may then be issued to or from a memory cell MC in the memory cell array 11 designated by the row address and column address. The read data DQ is output externally from the data terminals 24 via a read/write amplifier 15 and an input/output (IO) circuit 17. Similarly, when the write command is issued and a row address and a column address are timely supplied with the write command, and then write data DQ is supplied to the data terminals 24, the write data DQ is supplied via the input/output circuit 17 and the read/write amplifier 15 to the memory cell array 11 and written in the memory cell MC designated by the row address and the column address.

The input/output circuit 17 may include input buffers, according to one embodiment. The input/output circuit 17 receives external clock signals as a timing signal for determining input timing of write data DQ and output timing of read data DQ.

The power supply terminals 25 are supplied with power supply potentials VDD and VSS. These power supply potentials VDD and VSS are supplied to a voltage generator 39. The voltage generator 39 may generate various internal potentials VPP, VOD, VARY, VPERI, and the like based on the power supply potentials VDD and VSS. The internal potential VPP may be mainly used in the row decoder 12, the internal potentials VOD and VARY may be mainly used in the sense amplifiers 18 included in the memory cell array 11, and the internal potential VPERI may be used in many other circuit blocks.

Power supply potentials VDDQ and VSSQ are supplied to the input/output circuit 17. The power supply potentials VDDQ and VSSQ may be the same potentials as the power supply potentials VDD and VSS that are supplied to the power supply terminals 25, respectively. However, the dedicated power supply potentials VDDQ and VSSQ may be used for the input/output circuit 17 so that power supply noise generated by the input/output circuit 17 does not propagate to the other circuit blocks.

The input/output circuit 17 may also be coupled to an internal data strobe (DQS) generator circuit 14. The data strobe terminals 23 are supplied with external data strobe signals DQS and DQSB, respectively. These external data strobe signals DQS and DQSB are complementary to each other and are supplied to the internal data strobe (DQS) generator circuit 14. The internal data strobe (DQS) generator circuit 14 may generate a plurality of internal data strobe signals (e.g., Int DQS 0-3).

Referring back to the memory cell array 11, in certain embodiments, one or more phase driver circuits 36 may provide a refresh voltage (e.g., VCCP, approximately 3.3V, 3.0-3.8 V) to the word lines WL of the memory cell array 11 via one or more word line drivers (not shown). The word line drivers may receive the refresh voltage VCCP from the phase driver circuits 36 and refresh the respective memory cells using the refresh voltage VCCP.

By way of example, FIG. 2 illustrates a schematic diagram 40 of an example phase driver circuit 36 that is coupled to a number of word line drivers 42 and provides the refresh voltage VCCP to a number of corresponding word lines WL. As shown in FIG. 2, the phase driver circuit 36 may include two phase drivers 41 and 43. The phase driver 41 may include switches 44, 46, and 48, while the phase driver 43 may include switches 45, 47, and 49. The switches 44, 45, 46, 47, 48, and 49 may correspond to any suitable electronic switch that opens and closes based on a respective gate signal. As such, the switches 44, 45, 46, 47, 48, and 49 may include, but are not limited to, Metal Oxide Semiconductor Field Effect Transistors (MOSFETs), Insulated Gate Bipolar Transistors (IGBTs), and the like. Although the switches 44 and 45 are represented as a P-type switches and the switches 46, 47, 48, and 49 are represented as N-type switches, it should be noted that the embodiments described herein may be performed with any suitable arrangement of types of switches and thus are not limited to the arrangements described herein.

By way of operation, the phase driver 41 of the phase driver circuit 36 may receive a phase signal (RF0) to initiate a refresh operation on the memory cells connected to the word line drivers 42 associated with the respective phase driver circuit 36. In some embodiments, the phase signal (RF0) may be used during a refresh operation and/or during a row activation. That is, the phase signal (RF0) may be used to initiate a firing of a phase that occurs during both refresh and row activate commands. The phase signal RF0 may be a low voltage value, which may cause the switch 44 to close and the switch 48 to open. As a result, the refresh voltage VCCP may be electrically coupled to a phase driver output line 50, which may be electrically coupled to each word line driver 42.

Each word line driver 42 may receive a respective word line enable signal (WLF0-WLFN) at the gates of switches 52 and 54 of the word line driver 42. When the word line enable signal (WLF) corresponds to a low voltage (e.g., less than a threshold voltage for the respective switch 52/54), the switch 52 may close, thereby electrically coupling the phase driver output line 50 to a respective word line WL. As shown in FIG. 2, the phase driver output line 50 may provide the refresh voltage VCCP to a number of word line drivers 42. In this way, one phase driver circuit 36 may be used to provide power to a number of word line drivers 42 (e.g., refresh pumps). By using the same phase driver circuit 36 for multiple word line drivers 42 (e.g., refresh pumps), the semiconductor device 10 may conserve power as compared to the process of charging and discharging of each word line driver 42.

In addition, the phase driver 43 of the phase driver circuit 36 may receive a second phase signal (RF0F), which may be the opposite polarity of the phase signal (RF0), to release the respective word line driver 42 from ground or a negative word line voltage (Vnwl) and enable the respective word line driver 42 to be pulled to VCCP through the phase driver 41. In some embodiments, the second phase signal (RF0F) may be used to initiate the connection of the word line driver 42 to ground or the negative word line voltage (Vnwl). That is, the second phase signal RF0F may be a low voltage value, which may cause the switch 45 to close and the switch 49 to open. As a result, the refresh voltage VCCP may be electrically coupled to a word line switch 55, which may electrically couple to the output of a respective word line driver 42 to ground.

It should be noted that the various control signals (e.g., phase signal RF0, word line enable signal WLF, second phase signal RF0F) may be provided by a controller or control system that may be part of the semiconductor device 10. Indeed, the controller or control system may coordinate the refresh operations for the memory cells of the memory cell array 11 by transmitting the various control signals to coordinate the switching of the various switch components of the phase driver circuit 36, the word line driver 42, and the like.

Keeping the foregoing in mind, as the word line drivers 42 perform refresh operations over time, the refresh voltage VCCP may cause channel hot-carrier (CHC) degradation in n-MOS transistors, such as the switches 54 and 55 of the word line driver 42. That is, refresh voltage levels that exceed some threshold value may result in degradation of the switches in the word line drivers 42 and decrease the life of the respective memory device. To mitigate the CHC degradation of the components in the word line driver 42, a voltage selector circuit may be employed to use a certain voltage level for refresh operations. That is, when re-writing the same data back into a memory cell during a refresh operation, the word line driver 42 may use a lower voltage level, as compared to the higher voltage VCCP, used to write data in the respective memory cell during a write operation. As such, in some embodiments, the voltage selector circuit may reduce the amount of voltage provided to the phase driver circuit 36 during a refresh operation. In other words, the CHC degradation of components in the word line drivers 42 may occur by using the high VCCP level while keeping the phase driver circuit 36 on and cycling through different word line drivers 42. By employing the embodiments described herein, such as using the lower voltage level, the semiconductor device 10 may keep the phase driver circuit 36 on for the entire refresh period and cycle through several word line drivers 42 without exposing the components of the word line drivers 42 to the higher voltage VCCP.

For instance, FIG. 3 illustrates a schematic diagram 60 of a voltage selector circuit 62 that may provide the phase driver circuit 36 with two voltage supplies: the non-refresh voltage supply VCCP (e.g., 3.3V) or a low refresh voltage supply (VCCPLow) (e.g., approximately 2.8V, 2.5 V-2.9 V). By way of operation, the voltage selector signal may receive a Refresh signal and a RefreshF signal (e.g., via the controller or control system of the semiconductor device 10), which may be the inverse of the Refresh signal, at switches 64 and 66, respectively. The switch 64 may electrically couple the non-refresh voltage VCCP to the phase driver circuit 36, while the switch 66 may electrically couple the low refresh voltage VCCPLow to the phase driver circuit 36 as shown. In some embodiments, when the word line driver 42 is performing a refresh operation, the voltage selector circuit 62 may receive a high voltage value (e.g., greater than a threshold voltage for the respective switch) for the Refresh signal and a low voltage value for the RefreshF signal. As a result, the switch 64 may open and the switch 66 may close, thereby electrically coupling the low refresh voltage VCCPLow to the phase driver circuit 36. The phase driver circuit 36 may, in turn, provide the low refresh voltage VCCPLow to the word line drivers 42, as described above with respect to FIG. 2. In this way, one phase driver circuit 36 may be used to power a number of word line drivers 42 (e.g., refresh pumps), while providing a lower voltage level as compared to the non-refresh voltage VCCP.

Accordingly, the switches 52 and 54 may be better protected from CHC degradation due to the decreased voltage level provided by the low refresh voltage VCCPLow. Moreover, using the low refresh voltage VCCPLow may enable the semiconductor device 10 to use a single stage charge pump during the refresh operation, thereby increasing the efficiency of the use of the total current (IDD) provided to the word line drivers 42 to 90%.

With this in mind, FIG. 4 is a timing diagram 70 that illustrates an example operation related to the voltage selector circuit 62 providing phase driver output voltages at the non-refresh voltage VCCP or the low refresh voltage VCCPLow, in accordance with embodiments presented herein. As shown in FIG. 4, at time t₀, the Refresh signal may switch to high, the RefreshF signal may switch to low, and the phase signal RF0 may switch to low. As such, the phase driver output voltage may switch from low to high. It should be noted, however, that because the Refresh signal is high and the RefreshF signal is low, the voltage selector circuit 62 provides the low refresh voltage VCCPLow to the phase driver circuit 36.

After time t₀, the phase driver output voltage corresponds to the low refresh voltage VCCPLow and each of the connected word line drivers 42 receives the low refresh voltage VCCPLow via the phase driver output line 50. At this point in time, the phase driver output voltage may be equal to the low refresh voltage VCCPLow until the phase signal RF0 switches back to a high voltage at time t₉. As such, during this time period, the word line drivers 42 connected to the phase driver circuit 36 may be used to refresh the respective memory cells.

For example, between times t₁ and t₂, a first word line driver (WF0) may receive a word line enable signal (WLF0), which may involve switching from a high voltage value to a low voltage value. During this time period (e.g., between times t₁ and t₂), the word line 0 may receive the low refresh voltage VCCPLow to refresh the respective memory cells coupled thereto. In the same way, between times t₃ and t₄, a second word line driver (WF1) may receive a word line enable signal (WLF1), thereby providing word line 1 with the low refresh voltage VCCPLow to refresh the respective memory cells coupled thereto. This process is repeated for word line drivers WF2 and WF3, and thus may enable the phase driver circuit 36 to provide refresh power to four word line drivers 42, as opposed to switching the one phase driver circuit 36 on and off for each word line driver 42. It should be noted that the example operation described in FIG. 4 is provided with four word line drivers 42 for explanatory purposes, and any suitable number of word line drivers 42 may be coupled to the phase driver circuit 36, according to the embodiments described herein.

In addition to cycling through the word line enable signals (e.g., WLF0, WLF1) when the phase driver refresh signal RF0 is provided to the phase driver circuit 36, in some embodiments, the Refresh signal and the RefreshF signal may be pulsed to inverse voltages in between word line enable signals (WLFN) being provided to the word line drivers 42. As a result, the phase driver voltage output may decrease to eliminate the reliability risk on the switches 52 and 54 of the word line driver 42. That is, the phase driver voltage output swings between 2.8V and 3.3V, as opposed to between 0 and 3.3 V when the phase driver circuit 36 switches between off and on. The reduced voltage level of 2.8 v, as compared to 3.3V, would help protect the circuit components of the word line driver 42 from degrading while switching. That is, reducing the voltage from 3.3 V to 2.8 V removes degradation risk by limiting the voltage swing from 3.3 V to 0.5 V in between refresh pumps saves power.

With this in mind, FIG. 5 is a timing diagram 80 that illustrates how cycling through providing the Refresh and RefreshF signals to the voltage selector circuit 62 helps reduce the voltage swing of the phase driver voltage output. Referring to FIG. 5, at time t₀, the first word line enable signal WLF0 may be provided to the respective word line driver 42. At time t₁, the phase signal RF0 may be provided to the phase driver circuit 36. In addition, the Refresh signal may transition from a high voltage to a low voltage and the RefreshF signal may transition to a high voltage.

Since the Refresh signal is a low voltage and the RefreshF signal is a high voltage, the phase driver circuit 36 receives the refresh voltage VCCP (e.g., 3.3V), which is provided to the word line driver 42 via the phase driver output line 50. As such, between times t1 and t2, when the word line enable signal WLF0 is provided to the word line driver 42, the phase driver voltage output may correspond to the voltage VCCP. At time t₂, the Refresh signal may transition to a high voltage and the RefreshF signal may transition to a low voltage. At time t3, the word line enable signal (WLF0) returns to a high voltage, thereby disconnecting the respective word line driver 42 from the phase driver output line 50.

At time t₄, the second word line enable signal (WLF1) may be provided to a second word line driver 42. Between times t₃ and t₄, the voltage selector circuit 62 may output the low refresh voltage VCCPLow to the phase driver circuit 36. As such, the voltage provided to the word line driver 42 corresponds to the low refresh voltage VCCPLow. When the Refresh signal and the RefreshF signal return to the low voltage and the high voltage, respectively, at time t₅, the second word line driver 42 may receive the refresh voltage VCCP via the phase driver circuit 36. As a result, the word line driver 42 may receive voltages via the phase driver output line 50 that swing between the refresh voltage VCCP and the low refresh voltage VCCPLow, instead of between zero and some other voltage. Similar operations may be performed for the other word line drivers 42 that are coupled to the phase driver circuit 36, as described above, to control the voltage swing provided to the word line drivers 42.

By limiting the voltage swing that is exposed to the components of the word line driver 42, the operation of the voltage selector circuit 62, the phase driver circuit 36, and the word line driver 42, as described with respect to FIG. 5, the presently disclosed embodiments may save power by avoiding switching the phase driver circuit 36 off and on for each word line driver 42, while reducing the wear and degradation of the circuit components of the word line driver 42.

It should be noted that the refresh voltage VCCP is pulled down to the low refresh voltage VCCPLow using certain control signals provided to the various circuit components, as described above with respect to FIG. 5. However, it should also be noted that other control techniques (e.g., timing of control signals) may be employed to control the voltage swing provided to the word line drivers 42. Indeed, the presently disclosed techniques should not be limited to the embodiment described in FIG. 5. Instead, any suitable manner in which the voltage swing provided to the phase driver output line 50 may be employed using one phase driver circuit 36 for a number of word line drivers 42.

While the present disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the present disclosure is not intended to be limited to the particular forms disclosed. Rather, the present disclosure is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the following appended claims.

The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function] . . . ” or “step for [perform]ing [a function] . . . ”, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f). 

What is claimed is:
 1. A memory device, comprising: a phase driver circuit configured to output a first voltage for refreshing a plurality of memory cells; and a plurality of word line driver circuits configured to receive the first voltage via the phase driver circuit, wherein each word line driver circuit of the plurality of word line driver circuits is configured to provide the first voltage to a respective word line associated with a respective portion of the plurality of memory cells, and wherein each word line driver circuit is configured to refresh the respective portion of the plurality of memory cells based on a respective word line enable signal provided to a first switch of the respective word line driver circuit.
 2. The memory device of claim 1, comprising a voltage selector circuit configured to output a second voltage or a third voltage to the phase driver circuit based on a refresh input signal, wherein the third voltage is less than the second voltage, and wherein the first voltage output to the plurality of word line driver circuits corresponds to either the second voltage or the third voltage.
 3. The memory device of claim 2, wherein the second voltage comprises approximately 3.3 V and the third voltage comprises approximately 2.8 V.
 4. The memory device of claim 2, wherein the refresh input signal is provided to a second switch of the voltage selector circuit, and wherein the second switch is configured to couple the second voltage to the phase driver circuit based on the refresh input signal.
 5. The memory device of claim 2, wherein the voltage selector circuit comprises a third switch configured to couple the third voltage to the phase driver circuit based on an additional refresh input signal.
 6. The memory device of claim 5, wherein the additional refresh input signal is an inverse of the refresh input signal.
 7. The memory device of claim 2, wherein the voltage selector circuit is configured to output the third voltage to the phase driver circuit during a refresh operation for the plurality of memory cells.
 8. The memory device of claim 2, wherein each of the plurality of word line driver circuits is configured to receive the respective word line enable signal while the voltage selector circuit outputs the third voltage to the phase driver circuit.
 9. The memory device of claim 2, wherein each of the plurality of word line driver circuits is configured to receive the respective word line enable signal during a respective time period of a plurality of time periods, wherein each respective time period is distinct from other time periods of the plurality of time periods.
 10. A semiconductor device comprising: a memory cell array comprising a plurality of memory cells and a plurality of word lines; a voltage selector circuit configured to output a first voltage based on a refresh input signal or a second voltage based on an inverse of the refresh input signal, wherein the second voltage is less than the first voltage; a phase driver circuit configured to receive the first voltage or the second voltage from the voltage selector circuit, wherein the first voltage or the second voltage is configured to refresh the plurality of memory cells via the plurality of word lines; and a plurality of word line driver circuits configured to receive the first voltage or the second voltage via the phase driver circuit, wherein each word line driver circuit of the plurality of word line driver circuits is configured to provide the first voltage or the second voltage to a respective word line of the plurality of word lines associated with a respective portion of the plurality of memory cells.
 11. The semiconductor device of claim 10, wherein each word line driver circuit of the plurality of word line driver circuits is configured to receive a respective word line enable signal, wherein the respective word line enable signal is configured to cause a respective switch to close and provide the first voltage or the second voltage to the respective word line.
 12. The semiconductor device of claim 10, wherein each word line driver circuit of the plurality of word line driver circuits is configured to receive a respective word line enable signal, and wherein the refresh input signal is configured to transition between a high voltage and a low voltage or between the low voltage and the high voltage during a time period between each respective word line enable signal being provided to a respective word line driver circuit.
 13. The semiconductor device of claim 12, wherein each word line driver circuit of the plurality of word line driver circuits is configured to be exposed to a voltage swing between the first voltage and the second voltage during a time period between each respective word line enable input signal being provided to a respective word line driver circuit.
 14. The semiconductor device of claim 10, wherein the first voltage is within a first range of 3.0 to 3.5 V and the second voltage is within a second range of 2.5 V to 2.9 V.
 15. The semiconductor device of claim 14, wherein the voltage selector circuit comprises: a first switch configured to couple the first voltage to the phase driver circuit based on the refresh signal; and a second switch configured to couple the second voltage to the phase driver circuit based on inverse of the refresh signal.
 16. The semiconductor device of claim 10, wherein the voltage selector circuit is configured to output the second voltage while the plurality of word line driver circuits is performing a refresh operation for the plurality of memory cells.
 17. A method, comprising: receiving, via circuitry, a first refresh signal configured to cause a first switch to close, wherein the first switch is configured to couple a first voltage source to a phase driver circuit; receiving, via the circuitry, a second refresh signal configured to cause a second switch to close, wherein the second switch is configured to couple a second voltage source to the phase driver circuit, wherein the first voltage source is configured to provide a first voltage greater than a second voltage provided by the second voltage source; and receiving, via the circuitry, a phase signal configured to cause the phase driver circuit to selectively output the first voltage or the second voltage to a plurality of word line drivers configured to refresh a plurality of memory cells.
 18. The method of claim 17, comprising receiving, via the circuitry, a plurality of word line enable signals at the plurality of word line drivers, wherein each of the plurality of word line enable signals is configured to cause a respective word line driver of the plurality of word line drivers to provide the first voltage or the second voltage to a respective portion of the plurality of memory cells.
 19. The method of claim 18, wherein each of the plurality of word line enable signals is provided to the respective word line driver of the plurality of word line drivers during a different time period.
 20. The method of claim 19, wherein the second refresh signal is an inverse of the first refresh signal. 